Graphene-mediated microfluidic transport and nebulization via high frequency Rayleigh wave substrate excitation

Abstract

The deposition of a thin graphene film atop a chip scale piezoelectric substrate on which surface acoustic waves are excited is observed to enhance its performance for fluid transport and manipulation considerably, which can be exploited to achieve further efficiency gains in these devices. Such gains can then enable complete integration and miniaturization for true portability for a variety of microfluidic applications across drug delivery, biosensing and point-of-care diagnostics, among others, where field-use, point-of-collection or point-of-care functionality is desired. In addition to a first demonstration of vibration-induced molecular transport in graphene films, we show that the coupling of the surface acoustic wave gives rise to antisymmetric Lamb waves in the film which enhance molecular diffusion and hence the flow through the interstitial layers that make up the film. Above a critical input power, the strong substrate vibration displacement can also force the molecules out of the graphene film to form a thin fluid layer, which subsequently destabilizes and breaks up to form a mist of micron dimension aerosol droplets. We provide physical insight into this coupling through a simple numerical model, verified through experiments, and show several-fold improvement in the rate of fluid transport through the film, and up to 55% enhancement in the rate of fluid atomization from the film using this simple method.

Surface acoustic wave devices for chemical sensing and microfluidics: a review and perspective

“…125,126,127 As discussed above, there have been a large number of studies focused on a fundamental atomization mechanism, and much of the focus of recent work has been on engineering SAW atomization devices. 128,129,130 Further, some novel new applications have been developed including spray cooling 131 for thermal management, spray coating 132,133 , and even aerosolizing particles to load an optical trap. 134 However, in terms of chemical analysis and lab-on-a-chip applications, two primary applications have emerged and grown to near maturity.…”

Compact SAW aerosol generator

“…The existence of a fluid film in the SAW propagation path is essential for the aerosol droplet production, as fluid droplets with diameters between 0.1–100 μm are ejected from such a film (Ang et al, 2016 ; Collins et al, 2012 ; Wang et al, 2016 ). Commonly, the term „fluid film“ is defined as a body of fluid with a thickness that is substantially smaller than any of its horizontal dimensions.…”

Enhancing rate of water absorption in seeds via a miniature surface acoustic wave device

“…SAW devices have been used extensively for microfluidic operations and applications such as droplet transport and manipulation [13–16], fluid mixing [17,18], particle concentration [19–21], particle trapping and manipulation [22–25], liquid jetting [26] and atomization [27–30], cooling [31], heating [32], drug delivery [33,34] and nanofiltration [35]. When SAWs travel on the piezoelectric substrate, the surface displacement amplitude of the substrate is in the order of 10 −9 m, and the amplitude decays exponentially with increasing distance from the substrate surface.…”